Tag Archives: color management

Camera Calibration

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Custom Camera Calibration

The other day I had an email fall into my inbox from leading UK online retailer…whose name escapes me but is very short… that made my blood pressure spike.  It was basically offering me 20% off the cost of something that will revolutionise my photography – ColorChecker Passport Camera Calibration Profiling software.

I got annoyed for two reasons:

  1. Who the “f***” do they think they’re talking to sending ME this – I’ve forgotten more about this colour management malarkey than they’ll ever know….do some customer research you idle bastards and save yourselves a mauling!
  2. Much more importantly – tens of thousands of you guys ‘n gals will get the same email and some will believe the crap and buy it – and you will get yourselves into the biggest world of hurt imaginable!

Don’t misunderstand me, a ColorChecker Passport makes for a very sound purchase indeed and I would not like life very much if I didn’t own one.  What made me seethe is the way it’s being marketed, and to whom.

Profile all your cameras for accurate colour reproduction…..blah,blah,blah……..

If you do NOT fully understand the implications of custom camera calibration you’ll be in so much trouble when it comes to processing you’ll feel like giving up the art of photography.

The problems lie in a few areas:

First, a camera profile is a SENSOR/ASIC OUTPUT profile – think about that a minute.

Two things influence sensor/asic output – ISO and lens colour shift – yep. that’s right, no lens is colour-neutral, and all lenses produce colour shifts either by tint or spectral absorption. And higher ISO settings usually produce a cooler, bluer image.

Let’s take a look at ISO and its influence on custom camera calibration profiling – I’m using a far better bit of software for doing the job – “IN MY OPINION” – the Adobe DNG Profile Editor – free to all MAC download and Windows download – but you do need the ColorChecker Passport itself!

I prefer the Adobe product because I find the ColorChecker software produced camera calibration profiles there were, well, pretty vile in terms of increased contrast especially; not my cup of tea at all.

camera calibration, Andy Astbury, colour, color management

5 images shot at 1 stop increments of ISO on the same camera/lens combination.

Now this is NOT a demo of software – a video tutorial of camera profiling will be on my next photography training video coming sometime soon-ish, doubtless with a somewhat verbose narrative explaining why you should or should not do it!

Above, we have 5 images shot on a D4 with a 24-70 f2.8 at 70mm under a consistent overcast daylight at 1stop increments of ISO between 200 and 3200.

Below, we can see the resultant profile and distribution of known colour reference points on the colour wheel.

camera calibration, Andy Astbury, colour, color management

Here’s the 200 ISO custom camera calibration profile – the portion of interest to us is the colour wheel on the left and the points of known colour distribution (the black squares and circled dot).

Next, we see the result of the image shot at 3200 ISO:

camera calibration, Andy Astbury, colour, color management

Here’s the result of the custom camera profile based on the shot taken at 3200 ISO.

Now let’s super-impose one over t’other – if ISO doesn’t matter to a camera calibration profile then we should see NO DIFFERENCE………….

camera calibration, Andy Astbury, colour, color management

The 3200 ISO profile colour distribution overlaid onto the 200 ISO profile colour distribution – it’s different and they do not match up.

……..well would you bloody believe it!  Embark on custom camera calibration  profiling your camera and then apply that profile to an image shot with the same lens under the same lighting conditions but at a different ISO, and your colours will not be right.

So now my assertions about ISO have been vindicated, let’s take a look at skinning the cat another way, by keeping ISO the same but switching lenses.

Below is the result of a 500mm f4 at 1000 ISO:

camera calibration, Andy Astbury, colour, color management

Profile result of a 500mm f4 at 1000 ISO

And below we have the 24-70mm f2.8 @ 70mm and 1000 ISO:

camera calibration, Andy Astbury, colour, color management

Profile result of a 24-70mm f2.8 @ 70mm at 1000 ISO

Let’s overlay those two and see if there’s any difference:

camera calibration, Andy Astbury, colour, color management

Profile results of a 500mm f4 at 1000 ISO and the 24-70 f2.8 at 1000 ISO – as massively different as day and night.

Whoops….it’s all turned to crap!

Just take a moment to look at the info here.  There is movement in the orange/red/red magentas, but even bigger movements in the yellows/greens and the blues and blue/magentas.

Because these comparisons are done simply in Photoshop layers with the top layer at 50% opacity you can even see there’s an overall difference in the Hue and Saturation slider values for the two profiles – the 500mm profile is 2 and -10 respectively and the 24-70mm is actually 1 and -9.

The basic upshot of this information is that the two lenses apply a different colour cast to your image AND that cast is not always uniformly applied to all areas of the colour spectrum.

And if you really want to “screw the pooch” then here’s the above comparison side by side with with  the 500f4 1000iso against the 24-70mm f2.8 200iso view:

camera calibration, Andy Astbury, colour, color management

500mm f4/24-70mm f2.8 1000 ISO comparison versus 500mm f4 1000 ISO and 24-70mm f2.8 200 ISO.

A totally different spectral distribution of colour reference points again.

And I’m not even going to bother showing you that the same camera/lens/ISO combo will give different results under different lighting conditions – you should by now be able to envisage that little nugget yourselves.

So, Custom Camera Calibration – if you do it right then you’ll be profiling every body/lens combo you have, at every conceivable ISO value and lighting condition – it’s one of those things that if you don’t do it all then you’d be best off not doing at all in most cases.

I can think of a few instances where I would do it as a matter of course, such as scientific work, photo-microscopy, and artwork photography/copystand work etc, but these would be well outside the remit the more normal photographic practices.

As I said earlier, the Passport device itself is worth far more than it’s weight in gold – set up and light your shot and include the Passport device in a prominent place. Take a second shot without it and use shot 1 to custom white balance shot 2 – a dead easy process that makes the device invaluable for portrait and studio work etc.

But I hope by now you can begin to see the futility of trying to use a custom camera calibration profile on a “one size fits all” basis – it just won’t work correctly; and yet for the most part this is how it’s marketed – especially by third party retailers.

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Black Ink Type

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Black ink type and black ink switching when moving from matte to luster and gloss papers – here’s my thoughts on this, initially triggered by Franks’ reply to my previous article HERE.

And I quote:

Another great and instructive article Andy. I have the r3000 but get slightly annoyed with the black ink changes from one to the other. Some further guidance on the use of these re paper ‘types’ would be appreciated by moi ~ please ♡

Look, he’s even put a heart in there – bless you Frank, that’s more than I’ve got out of ‘her indoors’ for years!

Now the basic school of thought over this switching of black ink type is this:

  • PK, or Photo Black ink type supposedly produces a smooth, highly glossy black.
  • MK or Matte Black ink type produces a dull, flat black.
  • Using a matte finish paper requires the MATTE black ink type.
  • Using Luster or Gloss paper requires the Photo black ink type.

The PK black ink type really only produces a HIGH GLOSS finish when chucked onto HIGH GLOSS media.  Its’ got a rather less glossy and more ‘egg shell’ finish when used on a more luster finish paper. There does come a “tipping point” though where it will look a little shinier than the finish of the paper – and it’s this tipping point where theory, clever-dicks and user-guides tell you there’s a need to switch to the matte black ink type.

The Matte black ink type does exactly what point two says it does.

The third point – replace the word “requires” with the phrase “can cope with” and we’d be about right.

The forth point is absolutely true; get this wrong by printing with the MK black ink type on high gloss paper and you’ll just waste consumables and potentially end up with the type of clean up operation normally the preserve of Exon & BP. Dot gain on steroids!

There’s also an argument that the MK black ink type produces a deeper black on matte finish paper than the PK black ink type – this is also true:

printing,black ink,profile,icc profile,black ink type,matte finish,gloss finish,luster finish,

Permajet canned profiles for Museum paper on the Epson 4800 printer using PK and MK black ink types.

As we can clearly see, the Matte black ink type does indeed accommodate a deeper black point than its counterpart Photo black ink type.

Adopting the Common Sense Approach

There are a few things we need to think about here, and the first one is my constant mantra that the choice of paper is governed by the “overall look, feel and atmosphere of the finished image” when it’s sitting there on your monitor.

Paper choice IS the final part of the creative process; for all the reasons I’ve mentioned in past blog posts.

You will also know by now that in my world there is little room for high gloss paper – it’s a total pain the bum because of its highly reflective surface; but that same surface can allow you to print the very finest of details.

But here’s common sense point number 1 – the majority of people reading this blog, attending my workshops and coming to me for 1to1 tuition CAN NOT produce images with detail fine enough to warrant this single benefit of high gloss paper.

That’s not because they’re daft or rubbish at processing either – it’s simply due to the fact that they shoot 35mm format dSLR, not £30K medium format.  The sensors we commonly use can’t record enough ultra fine detail.  There’s a really good comparison between the Nikon D800 and an IQ160 here, it’s well worth having a look – then you’ll see what I’m on about.

The point I’m trying to make is this; print on gloss from 35mm if you like; but you are saddling yourself with its problems but not truthfully getting any of the benefit – but you can kid yourself if you like!

I Lust After Luster Papers But How Lusty Is That Luster?

As I mentioned in the previous post, Calumet Brilliant Museum Satin Matte Natural is NOT a matte finish paper.

True matte papers never really hold much appeal for me if I’m honest, because they are very dull, flat and relatively lifeless.  Yes, a 12×12 inch monochromatic image might look stunning, especially hanging in an area where reflections might prove difficult for any other print surface.

But that same image printed 8 foot square might well “kill’ any room you hang it in, just because it’s so dull and so damned BIG.

True matte papers do have their uses that’s for sure, but in the main you need to discriminate between matte and what I call matte “effect”.

Permajet Fine Art Museum 310, Matte Plus and Portrait 300 are papers that spring to mind as falling into this matte effect category – and wouldn’t you know it, there are canned profiles for these papers for both PK and MK black ink type ink sets, as you can see from the image earlier in the post.

So, with regard to black ink type switching you have to ask yourself:

  • Am I using a paper the ACTUALLY NEEDS the MK black ink type?  Chances are you’re probably not!
  • If I am, do I really want to – how big a print am I doing?

In my own print portfolio I only have two images that benefit from being printed on a “dead” media surface, and they are both printed to Permajet Museum using the PK black ink type.

I had another one that looked “nearly there” but the heavy texture of the paper detracted from the image, so it was re-proofed and printed to Matt Plus, again using PK ink. It looked just the same from a colour/luminance stand point, but worse from a ‘style’ point because of the zero texture.

Along comes Calumet Museum Satin Matte Natural!

The subtle texture gets me where I wanted to be on that score, and that ever-so-soft luster just makes the colours come to life that tiny bit more, giving me a print variation that I love and hadn’t even envisaged at the time I did the original print.

Ink Type Switching

I have to say at the outset that I do NOT own an R3000 printer – I use wide format Epson printers and so have no commercial need for the 3000 DT format.  But I always advise people looking for a printer to buy one – it’s a stunning machine that punches well above it’s weight based on price point.

My Epson wide format does not hold both black ink types.  Switching entails a rather tedious and highly wasteful process; which I have neither desire or need to embark upon.

But if you have any brand of printer that carries both types on board then I’d highly recommend you to set the black ink type to PK, and turn any auto-switching OFF – that is, set switching to manual.

Right, now the super-pessimist in me shines through!

I’m not a fan of Epson papers on the whole, and there’s a lot more choice and far better quality available from third party suppliers ranging from Photospeed to Hahnemuhle, Canson, Red River and all points in between.

Now third party suppliers in the main will tell you to use one black ink type or the other – or either, and give you the correct media settings (Brilliant – are you reading this??).

But, if you have auto switching enabled, and use Epson paper, the print head sees the paper surface and automatically switches the ink to the ‘supposed’ correct type.  This switching process requires the printer to purge the black ink line and refill it with the ‘correct’ black ink type before printing commences.

Now these figures are the stats quoted from Epson:

Black ink conversion times:

  • Matte to Photo Black approx. 3 min. 30 sec
  • Photo to Matte Black approx. 2 min. sec

Ink used during conversion:

  • Matte to Photo Black approx. 3 ml
  • Photo to Matte Black approx. 1 ml

Now why the times and volumes aren’t the same in both directions is a bit of a mystery to me and doesn’t make sense.  But what is killer is that the carts are only 26 (25.9)ml and around £24 each, so 6 changes of black ink type is going to burn through as good as £25 of ink – and that’s without doing any bloody printing!!!

When ever I demo this printer at a workshop I never use Epson paper, auto switching is OFF and I never get a head sensor warning to tell me to switch ink even if I load Permajet Museum – the head sensor doesn’t warn me about the fact that I’m using PK ink.

Yes the printer could be up the spout, but using a canned PK profile the resulting print would tend to indicate otherwise.

Or something slightly more dark and sinister might be happening – or rather NOT, because I’m not using OEM paper………...What was that I heard you say?  Good gracious me…you might think that but I couldn’t possibly comment!

One thing to bare in mind is this.  For the most part, the majority of print media will work exceptionally well with the PK black ink type – BUT NOT THE OTHER WAY AROUND – you’ve been warned.  If you want to know how the captain of the Exon Valdez felt and be up to your ass in black stuff then go ahead and give it a try, but don’t send the cleaning bills to me!

I did it once years ago with an HP printer – I can still see matte black ink tide marks on the skirting board in my office……it wasn’t pretty! And it screwed the printer up totally.

Using PK on matte media will only effect the D-max and lower the overall contrast a wee bit; unless it’s a very low key image with vast areas of blackish tones in it then for the most part you’d perhaps struggle to notice it.  Sometimes you might even find that the drop in contrast even works to your advantage.

But don’t forget, you might not be using a matte media at all, even though it visually looks like it and says the word matte in the paper name.  If the paper manufacturer supplies a PK and an MK profile for the same paper then save yourself time and money and use the PK profile to soft-proof to AND to control the printer colour management.

Did that answer your question Frank – FRANK – can you hear me Frank??!!

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Brilliant Papers from Calumet

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Brilliant Papers from Calumet

My thoughts on two papers from the Calumet Brilliant Papers range.

Brilliant Museum Printing Papers from Calumet,printing,brilliant papers,Calumet,desktop printing,printer papers,Andy Astbury

Brilliant Museum Printing Papers from Calumet

As I CONSTANTLY demonstrate to individuals and groups during workshops and 1to1 tuition days, printing is so damned easy it’s ridiculous.  Provided you get all your “ducks in a row” – and that’s not the hardest thing in the world to do, considering you’ve only got 3 bloody ducks!

How hard can it be???

Notwithstanding the necessity for an accurate monitor profile (duck number 1), the paper and its profile, or colour space if you like, form the back-bone of both “soft-proof” and the final print that spews forth from your printer – they’re ducks 2 and 3 respectively.

When getting someone on the “straight and narrow path to print righteousness” I always find it best practice to make them stick to one paper until they are super-familiar with the process, and begin to appreciate the fact that paper choice is the final step in the creative process.

I never want to confuse folk with custom profiles either – if I can get them onto a paper that comes supplied with a reliable OEM profile which includes the relevant MEDIA SETTINGS for the printer (these are crucial) then my work is done.

One paper with a very accurate OEM profile that has media settings as part of the profile name is Permajet Oyster 271.  A cracking paper for general purpose printing, it’s finish suits most images, and it’s still my go-to paper for prints of general wildlife and natural history subjects.

But it doesn’t suit everything, and landscapes, seascapes, and other styles of fine art imagery are the sorts of images that spring to mind.  It’s paper-white is a little on the cool side for starters – so printing a warm tone image to it increases your soft-proof workload for starters.

So I’m always trying different papers so that I can recommend them to my clients,  but no matter how good I find them, I’ll rarely recommend them if the supplied OEM profile is crap.  With the profiling gear I use I could get a workable custom profile for toilet paper if I had to, but telling someone new to printing that they need to:

  • Spend £1500 on the gear
  • Learn how to use what looks like the most scary software GUI on the planet
  • Waste 1 or 2 sheets of paper and ink printing the test charts (it’s not a waste really but that’s how they’d see it).

isn’t a real option.

But now I’m in love with two papers from Calumet and their Brilliant Papers Museum range.  They are:

  • Brilliant Papers Museum Satin Matte Natural

  • Brilliant Museum Printing Papers from Calumet,printing,brilliant papers,Calumet,desktop printing,printer papers,Andy Astbury

    Brilliant Papers Museum Inkjet Paper – Satin Matte Natural

  • Brilliant Papers Museum Silver Gloss Natural

  • Brilliant Museum Printing Papers from Calumet,printing,brilliant papers,Calumet,desktop printing,printer papers,Andy Astbury

    Brilliant Papers Museum Inkjet Paper – SilverGloss Natural

 

Both these papers, in my opinion, are up there with the very best of them.  And, while they cost – size for size – twice as much as something like Permajet Oyster; they are both far more than twice as beneficial to the easy production of fine art landscapes and other images that require a bit more from the printer paper to add the final touch.

I’ve used both papers on the Epson R3000 with the Epson ink set, and on my Epson 4800 that carries a Lyson ink set, and all I can say is that I’m more than impressed, and have no trouble in recommending you give them a go.

On the Epson R3000 I used the “canned profiles” downloadable from Brilliant Papers website HERE  but you need to understand that Brilliant have not exactly been sensible here and have omitted to give you any indication of correct media settings.

I’ve actually been using media settings of WCRW (water colour radiant white) for the Satin Matte Natural on the R3000 and TFAP (textured fine art paper) on the 4800.

For the Silver Gloss Natural the media settings for both printers have been UPPPL (ultra premium photo paper lustre) and results have been superb.

Just in case you don’t understand why media settings need to be set correctly, different papers require, amongst other things, different inking levels from the print head – too much ink and the print will look dark, too little and it’ll look pale and washed out.  There is also the little matter of what’s called “dot gain”.  Some papers have a hard glossy surface, others a more rough and porous one. A nozzle droplet of a particular size might be fine on a gloss paper, but that same size droplet on a fine art rag paper might well ‘bleed’ and spread out like it was on blotting paper.  This bleeding, or dot gain, leads to a reduction in sharpness of fine detail.

So, media settings are important – they ain’t there for the hell of it you know!

The “canned” profiles plot for the Epson R3000 using MK ink for Satin Matte Natural and PK ink for the Silver Gloss Natural (sRGB included for comparison):

Brilliant Museum Printing Papers from Calumet,printing,brilliant papers,Calumet,desktop printing,printer papers,Andy Astbury

Click to enlarge

And for the 4800:

Brilliant Museum Printing Papers from Calumet,printing,brilliant papers,Calumet,desktop printing,printer papers,Andy Astbury

Click to enlarge

I swapped the plot colours around by mistake – my bad!

I always used to like the look of images printed on Permajets Fine Art Museum 310, but 90% of the time I felt the texture somehow visually ‘got in the way’.

The texture of Brilliant Papers Museum Satin Matte Natural is not quite so pronounced which means I like it better!

In practical terms the colour space of the paper, though ever so slightly smaller than the Permajet Museum paper, does give you slightly deeper blacks and that tiny bit of extra shadow detail clarity.  All in all, a very good go-to paper, especially for the more monochromatic image such as:

printing,brilliant papers,Calumet,desktop printing,printer papers,Andy Astbury

“The Portal”

The Brilliant Papers Silver Gloss Natural.  I find it difficult to actually describe the finish as “gloss” – it’s more like a very fine grained lustre to be honest.

And the difference between the two papers?  Well, the Silver Gloss just has that little extra contrast in the medium and darker midtones – it’s a bit like adding 8 or 10 points of clarity to an image inside of the Lightroom Dev module.  I’d definitely consider this a great paper for landscape and fine art imagery that contains just that little bit more in terms of colour variation and saturation:

printing,brilliant papers,Calumet,desktop printing,printer papers,Andy Astbury

“Stepping Stones to Oblivion”

All in all two very nice papers from the Brilliant Papers range that will be seeing regular use both in my own work, and in my workshops and tuition days; though not exactly budget-priced papers they’re no where near as pricey as some – plus, don’t you think your images are worth it?

And just in case you were wondering; I too was quite surprised at just how well matched the Brilliant canned profiles for the 4800 worked out on my Lyson ink set! I’ve written custom profiles for both of these papers, and there is generally so little difference between the custom and Brilliant profiles (which are really intended for the Epson ink set) that I can’t tell the difference between the prints I’ve done so far – and I’ve done a few!

Though for my own printing I’ll always use my custom icc profiles.

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Paper White – Desktop Printing 101

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Paper White video

A while back I posted an article called How White is Paper White

As a follow-up to my last post on the basic properties of printing paper media I thought I’d post this video to refresh the idea of “white”.

In this video we basically look at a range of 10 Permajet papers and simply compare their tints and brightness – it’s an illustration I give at my print workshops which never fails to amaze all the attendees.

I know I keep ‘banging on’ about this but you must understand:

  • Very few paper whites are even close to being neutral.
  • No paper is WHITE in terms of luminosity – RGB 255 in 8 bit colour terms.
  • No paper can hold a true black – RGB 0 in 8 bit colour terms.

In real-world terms ALL printing paper is a TINTED GREY – some cool, some warm.

printing,paper white,desktop printing,Andy Astbury,Wildlife in Pixels

If we attempted to print the image above on a cool tinted paper then we would REDUCE or even CANCEL OUT the warm tonal effects and general ‘atmosphere’ of the image.

Conversely, print it to a warmer tinted ‘paper white’ and the atmosphere would be enhanced.

Would this enhancement be a good thing?  Well, er NO – not if we were happy with our original ‘on screen’ processing.

You need to look upon ‘paper white’ as another TOOL to help you achieve your goal of great looking photographs, with a minimum of fuss and effort on your part.

We have to ‘soft proof’ our images if we want to get a print off the printer that matches what we see on our monitor.

But we can’t soft proof until we have made a decision about what paper we are going to soft-proof to.

Choosing a paper who’s characteristics match our finished ‘on screen’ image in terms of TINT especially, will make the job of soft proofing much easier.

How, why?

Proper soft proofing requires us to make a copy of our original image (there’s most peoples first mistake – not making a copy) and then making adjustments to said copy, in a soft proof environment, so that it it renders correctly on the print – in other words it matches our original processed image.

Printing from Photoshop requires a hard copy, printing from Lightroom is different – it relies on VIRTUAL copies.

Either way, this copy and its proof adjustments are what get sent to the printer along what we call the PRINT PIPELINE.

The print pipeline has to do a lot of work:

  • It has to transpose our adjusted/soft proofed image colour values from additive RGB to print CMYK
  • It has to up sample or interpolate the image dpi instructions to the print head, depending on print output size.
  • It has to apply the correct droplet size instructions to each nozzle in the print head hundreds of times per second.
  • And it has to do a lot of other ‘stuff’ besides!!

The key component is the Printer Driver – and printer drivers are basically CRAP at carrying out all but the simplest of instructions.

In other words they don’t like hard work.

Printing to a paper white that matches our image:

  • Warm image to warm tint paper white
  • Cool image to cool paper white

will reduce to the amount of adjustments we have to make under soft proofing and therefore REDUCE the printer driver workload.

The less work the print driver has to do, the lower is the risk of things  ‘getting lost in translation‘ and if nothing gets lost then the print matches the on screen image – assuming of course that your eyes haven’t let you down at the soft proofing stage!

print,desktop printing,paper white

IMPORTANT – Click Image to Enlarge in new window

If we try to print this squirrel on the left to Permajet Gloss 271 (warmish image to very cool tint paper white) we can see what will happen.

We have got to make a couple of tweaks in terms on luminosity BUT we’ve also got to make a global change to the overall colour temperature of the image – this will most likely present us with a need for further  opposing colour channel adjustments between light and dark tones.

 

print,desktop printing,paper white

IMPORTANT – Click Image to Enlarge in new window

Whereas the same image sent to Permajet Fibre Base Gloss Warmtone all we’ll have to do is tweak the luminosity up a tiny bit and saturation down a couple of points and basically we’ll be sorted.

So less work, and less work means less room for error in our hardware drivers; this leads to more efficient printing and reduced print production costs.

And reduced cost leads to a happy photographer!

Printing images is EASY –  as long as you get all your ducks in a row – and you’ve only got a handful of ducks to control.

Understanding print media and grasping the implications of paper white is one of those ducks………

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Desktop Printing 101

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Understanding Desktop Printing – part 1

 

desktop printingDesktop printing is what all photographers should be doing.

Holding a finished print of your epic image is the final part of the photographic process, and should be enjoyed by everyone who owns a camera and loves their photography.

But desktop printing has a “bad rap” amongst the general hobby photography community – a process full of cost, danger, confusion and disappointment.

Yet there is no need for it to be this way.

Desktop printing is not a black art full of ‘ju-ju men’ and bear-traps  – indeed it’s exactly the opposite.

But if you refuse to take on board a few simple basics then you’ll be swinging in the wind and burning money for ever.

Now I’ve already spoken at length on the importance of monitor calibration & monitor profiling on this blog HERE and HERE so we’ll take that as a given.

But in this post I want to look at the basic material we use for printing – paper media.

Print Media

A while back I wrote a piece entitled “How White is Paper White” – it might be worth you looking at this if you’ve not already done so.

Over the course of most of my blog posts you’ll have noticed a recurring undertone of contrast needs controlling.

Contrast is all about the relationship between blacks and whites in our images, and the tonal separation between them.

This is where we, as digital photographers, can begin to run into problems.

We work on our images via a calibrated monitor, normally calibrated to a gamma of 2.2 and a D65 white point.  Modern monitors can readily display true black and true white (Lab 0 to Lab 100/RGB 0 to 255 in 8 bit terms).

Our big problem lies in the fact that you can print NEITHER of these luminosity values in any of the printer channels – the paper just will not allow it.

A papers ability to reproduce white is obviously limited to the brightness and background colour tint of the paper itself – there is no such think as ‘white’ paper.

But a papers ability to render ‘black’ is the other vitally important consideration – and it comes as a major shock to a lot of photographers.

Let’s take 3 commonly used Permajet papers as examples:

  • Permajet Gloss 271
  • Permajet Oyster 271
  • Permajet Portrait White 285

The following measurements have been made with a ColorMunki Photo & Colour Picker software.

L* values are the luminosity values in the L*ab colour space where 0 = pure black (0RGB) and 100 = pure white (255RGB)

Gloss paper:

  • Black/Dmax = 4.4 L* or 14,16,15 in 8 bit RGB terms
  • White/Dmin = 94.4 L* or 235,241,241 (paper white)

From these measurements we can see that the deepest black we can reproduce has an average 8bit RGB value of 15 – not zero.

We can also see that “paper white” has a leaning towards cyan due to the higher 241 green & blue RGB values, and this carries over to the blacks which are 6 points deficient in red.

Oyster paper:

  • Black/Dmax = 4.7 L* or 15,17,16 in 8 bit RGB terms
  • White/Dmin = 94.9 L* or 237,242,241 (paper white)

We can see that the Oyster maximum black value is slightly lighter than the Gloss paper (L* values reflect are far better accuracy than 8 bit RGB values).

We can also see that the paper has a slightly brighter white value.

Portrait White Matte paper:

  • Black/Dmax = 25.8 L* or 59,62,61 in 8 bit RGB terms
  • White/Dmin = 97.1 L* or 247,247,244 (paper white)

You can see that paper white is brighter than either Gloss or Oyster.

The paper white is also deficient in blue, but the Dmax black is deficient in red.

It’s quite common to find this skewed cool/warm split between dark tones and light tones when printing, and sometimes it can be the other way around.

And if you don’t think there’s much of a difference between 247,247,244 & 247,247,247 you’d be wrong!

The image below (though exaggerated slightly due to jpeg compression) effectively shows the difference – 247 neutral being at the bottom.

paper white,printing

247,247,244 (top) and 247,247,247 (below) – slightly exaggerated by jpeg compression.

See how much ‘warmer’ the top of the square is?

But the real shocker is the black or Dmax value:

paper,printing,desktop printing

Portrait White matte finish paper plotted against wireframe sRGB on L*ab axes.

The wireframe above is the sRGB colour space plotted on the L*ab axes; the shaded volume is the profile for Portrait White.  The sRGB profile has a maximum black density of 0RGB and so reaches the bottom of vertical L axis.

However, that 25.8 L* value of the matte finish paper has a huge ‘gap’ underneath it.

The higher the black L* value the larger is the gap.

What does this gap mean for our desktop printing output?

It’s simple – any tones in our image that are DARKER, or have a lower L* value than the Dmax of the destination media will be crushed into “paper black” – so any shadow detail will be lost.

Equally the same can be said for gaps at the top of the L* axis where “paper white” or Dmin is lower than the L* value of the brightest tones in our image – they too will get homogenized into the all-encompassing paper white!

Imagine we’ve just processed an image that makes maximum use of our monitors display gamut in terms of luminosity – it looks magnificent, and will no doubt look equally as such for any form of electronic/digital distribution.

But if we send this image straight to a printer it’ll look really disappointing, if only for the reasons mentioned above – because basically the image will NOT fit on the paper in terms of contrast and tonal distribution, let alone colour fidelity.
It’s at this point where everyone gives up the idea of desktop printing:

  • It looks like crap
  • It’s a waste of time
  • I don’t know what’s happened.
  • I don’t understand what’s gone wrong

Well, in response to the latter, now you do!

But do we have to worry about all this tech stuff ?

No, we don’t have to WORRY about it – that’s what a colour managed work flow & soft proofing is for.

But it never hurts to UNDERSTAND things, otherwise you just end up in a “monkey see monkey do” situation.

And that’s as dangerous as it can get – change just one thing and you’re in trouble!

But if you can ‘get the point’ of this post then believe me you are well on your way to understanding desktop printing and the simple processes we need to go through to ensure accurate and realistic prints every time we hit the PRINT button.

desktop printing

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Gamma Encoding – Under the Hood

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Gamma, Gamma Encoding & Decoding

Gamma – now there’s a term I see cause so much confusion and misunderstanding.

So many people use the term without knowing what it means.

Others get gamma mixed up with contrast, which is the worst mistake anyone could ever make!

Contrast controls the spatial relationship between black and white; in other words the number of grey tones.  Higher contrast spreads black into the darker mid tones and white into the upper mid tones.  In other words, both the black point and white point are moved.

The only tones that are not effected by changes in image gamma are the black point and white point – that’s why getting gamma mixed up with contrast is the mark of a “complete idiot” who should be taken outside and summarily shot before they have chance to propagate this shocking level of misunderstanding!

What is Gamma?

Any device that records an image does so with a gamma value.

Any device which displays/reproduces said image does so with a gamma value.

We can think of gamma as the proportional distribution of tones recorded by, or displayed on, a particular device.

Because different devices have different gamma values problems would arise were we to display an image that has a gamma of X on a display with a gamma of Y:

Ever wondered what a RAW file would look like displayed on a monitor without any fancy colour & gamma managed software such as LR or ACR?

gamma,gamma encoding,Andy Astbury

A raw file displayed on the back of the camera (left) and as it would look on a computer monitor calibrated to a gamma of 2.2 & without any colour & gamma management (right).

The right hand image looks so dark because it has a native gamma of 1.0 but is being displayed on a monitor with a native gamma of 2.2

RAW file Gamma

To all intents and purposes ALL RAW files have a gamma of 1.0

gamma,gamma encoding,Andy Astbury

Camera Sensor/Linear Gamma (Gamma 1.0)

Digital camera sensors work in a linear fashion:

If we have “X” number of photons striking a sensor photosite then “Y” amount of electrons will be generated.

Double the number of photons by doubling the amount of light, then 2x “Y” electrons will be generated.

Halve the number of photons by reducing the light on the scene by 50% then 0.5x “Y” electrons will be generated.

We have two axes on the graph; the horizontal x axis represents the actual light values in the scene, and the vertical y axis represents the output or recorded tones in the image.

So, if we apply Lab L* values to our graph axes above, then 0 equates to black and 1.0 equates to white.

The “slope” of the graph is a straight line giving us an equal relationship between values for input and output.

It’s this relationship between input and output values in digital imaging that helps define GAMMA.

In our particular case here, we have a linear relationship between input and output values and so we have LINEAR GAMMA, otherwise known as gamma 1.0.

Now let’s look at a black to white graduation in gamma 1.0 in comparison to one in what’s called an encoding gamma:

gamma,gamma encoding,Andy Astbury

Linear (top) vs Encoded Gamma

The upper gradient is basically the way our digital cameras see and record a scene.

There is an awful lot of information about highlights and yet the darker tones and ‘shadow’ areas are seemingly squashed up together on the left side of the gradient.

Human vision does not see things in the same way that a camera sensor does; we do not see linearly.

If the amount of ambient light falling on a scene suddenly doubles we will perceive the increase as an unquantifiable “it’s got brighter”; whereas our sensors response will be exactly double and very quantifiable.

Our eyes see a far more ‘perceptually even’ tonal distribution with much greater tonal separation in the darker tones and a more compressed distribution of highlights.

In other words we see a tonal distribution more like that contained in the gamma encoded gradient.

Gamma encoding can be best illustrated with another graph:

gamma,gamma encoding,Andy Astbury

Linear Gamma vs Gamma Encoding 1/2.2 (0.4545)

Now sadly this is where things often get misunderstood, and why you need to be careful about where you get information from.

The cyan curve is NOT gamma 2.2 – we’ll get to that shortly.

Think of the graph above as the curves panel in Lightroom, ACR or Photoshop – after all, that’s exactly what it is.

Think of our dark, low contrast linear gamma image as displayed on a monitor – what would we need to do to the linear slope  to improve contrast and generally brighten the image?

We’d bend the linear slope to something like the cyan curve.

The cyan curve is the encoding gamma 1/2.2.

There’s a direct numerical relationship between the two gamma curves; linear and 1/2.2. and it’s a simple power law:

  •  VO = VIγ where VO = output value, VI = input value and γ = gamma

Any input value (VI) on the linear gamma curve to the power of γ equals the output value of the cyan encoding curve; and γ as it works out equals 0.4545

  •  VI 0 = VO 0
  •  VI 0.25 = VO 0.532
  •  VI 0.50 = VO 0.729
  •  VI 0.75 = VO 0.878
  •  VI 1.0 = VO 1.0

Now isn’t that bit of maths sexy………………..yeah!

Basically the gamma encoding process remaps all the tones in the image and redistributes them in a non-linear ratio which is more familiar to our eye.

Note: the gamma of human vision is not really gamma 1/2.2 – gamma 0.4545.  It would be near impossible to actually quantify gamma for our eye due to the behavior of the iris etc, but to all intents and purposes modern photographic principles regard it as being ‘similar to’..

So the story so far equates to this:

gamma,gamma encoding,Andy Astbury

Gamma encoding redistributes tones in a non-linear manner.

But things are never quite so straight forward are they…?

Firstly, if gamma < 1 (less than 1) the encoding curve goes upwards – as does the cyan curve in the graph above.

But if gamma > 1 (greater than 1) the curve goes downwards.

A calibrated monitor has (or should have) a calibrated device gamma of 2.2:

gamma,gamma encoding,Andy Astbury

Linear, Encoding & Monitor gamma curves.

As you can now see, the monitor device gamma of 2.2 is the opposite of the encoding gamma – after all, the latter is the reciprocal of the former.

So what happens when we apply the decoding gamma/monitor gamma of 2.2 to our gamma encoded image?

gamma,gamma encoding,Andy Astbury

The net effect of Encode & Decode gamma – Linear.

That’s right, we end up back where we started!

Now, are you thinking:

  • Don’t understand?
  • We are back with our super dark image again?

Welcome to the worlds biggest Bear-Trap!

The “Learning Gamma Bear Trap”

Hands up those who are thinking this is what happens:

gamma,gamma encoding,Andy Astbury

If your arm so much as twitched then you are not alone!

I’ll admit to being naughty and leading you to edge of the pit containing the bear trap – but I didn’t push you!

While you’ve been reading this post have you noticed the occasional random bold and underlined text?

Them’s clues folks!

The super dark images – both seascape and the rope coil – are all “GAMMA 1.0 displayed on a GAMMA 2.2 device without any management”.

That doesn’t mean a gamma 1.0 RAW file actually LOOKS like that in it’s own gamma environment!

That’s the bear trap!

gamma,gamma encoding,Andy Astbury

Gamma 1.0 to gamma 2.2 encoding and decoding

Our RAW file actually looks quite normal in its own gamma environment (2nd from left) – but look at the histogram and how all those darker mid tones and shadows are piled up to the left.

Gamma encoding to 1/2.2 (gamma 0.4545) redistributes and remaps those all the tones and lightens the image by pushing the curve up BUT leaves the black and white points where they are.  No tones have been added or taken away, the operation just redistributes what’s already there.  Check out the histogram.

Then the gamma decode operation takes place and we end up with the image on the right – looks perfect and ready for processing, but notice the histogram, we keep the encoding redistribution of tones.

So, are we back where we started?  No.

Luckily for us gamma encoding and decoding is all fully automatic within a colour managed work flow and RAW handlers such as Lightroom, ACR and CapOnePro etc.

Image gamma changes are required when an image is moved from one RGB colour space to another:

  • ProPhoto RGB has a gamma of 1.8
  • Adobe RGB 1998 has a gamma of 2.2
  • sRGB has an oddball gamma that equates to an average of 2.2 but is nearly 1.8 in the deep shadow tones.
  • Lightrooms working colour space is ProPhoto linear, in other words gamma 1.0
  • Lightrooms viewing space is MelissaRGB which equates to Prophoto with an sRGB gamma.

Image gamma changes need to occur when images are sent to a desktop printer – the encode/decode characteristics are actually part and parcel of the printer profile information.

Gamma awareness should be exercised when it comes to monitors:

  • Most plug & play monitors are set to far too high a gamma ‘out the box’ – get it calibrated properly ASAP; it’s not just about colour accuracy.
  • Laptop screen gamma changes with viewing position – God they are awful!

Anyway, that just about wraps up this brief explanation of gamma; believe me it is brief and somewhat simplified – but hopefully you get the picture!

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Photoshop CC Update

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Photoshop CC Update

Installing a new Photoshop CC update is supposed to be a simple matter of clicking a button and the job gets done.

This morning both my Mac systems were telling me to update from v14.1.2 to v14.2

I have two Macs, a late 2012 iMac and a mid 2009 Mac Pro.  The Mac Pro used to run Snow Leopard but was upgraded to Mountain Lion because of Lightroom 5 dropping Snow Leopard support.

Now I never have any problems with Cloud Updates from Adobe on the iMac, but sometimes the Mac Pro can do some strange things – and this morning was no exception!

The update installed on the iMac without a hitch, but when the update was complete on the Mac Pro I was greeted with a message telling me that some components had not installed correctly.  On opening Photoshop CC I was greeted with the fact that the version had rolled back to v14.0 and that hitting UPDATE in both the app and my CC control panel simply informed me that my software was up to date and no updates were available!

So I just thought I’d do a blog entry on what to do if this ever happens to you!

 

Remove Photoshop CC

The first thing to do is UNINSTALL  Photoshop CC with the supplied uninstaller.

You’ll find this in the main Photoshop CC root directory:

Photoshop CC Update

Locate the Photoshop CC Uninstaller.

Take my advice and put a tick in the check box to “Remove Preferences” – the Photoshop preferences file can be a royal pain in the ass sometimes, so dump it – a new one will get written as soon as your fire Photoshop up after the new install.

Click UNINSTALL.

Once this action is complete YOU MUST RESTART THE MACHINE.

 

After the restart wait for the Creative Cloud to connect then open your CC control panel.

Under the Apps tab you’ll see that Photoshop CC is no longer listed.

Scroll down past all the apps Adobe have listed and you’ll come to Photoshop CC;  it’ll have an INSTALL button next to it – click the install button:

Photoshop CC Update

Install Photoshop CC from the Cloud control panel.

If you are installing the 14.1.2 to 14.2 update (the current one as of today’s date) you might find a couple of long ‘stick bits’ during the installation process – notably between 1 and 20% and a long one at 90% – just let the machine do it’s thing.

When the update is complete I’d recommend you do a restart – it might not be necessary, but I do it anyway.

Once the machine has restarted fire up Photoshop, click on ‘About Photoshop’ and you should see:

Photoshop CC Update

Photoshop “about screen” showing version number.

Because we dumped the preferences file we need to go and change the defaults for best best working practice:

Photoshop CC Update

Preferences Interface tab.

If you want to change the BG colour then do it here.

Next, click File Handling:

Photoshop CC Update

File handling tab in Photoshop Preferences

Remove the tick from the SAVE IN BACKGROUND check box – like the person who put it there, you too might think background auto-save is a good idea – IT ISN’T – think about it!

Finally, go to Performance:

Photoshop CC Update

Photoshop preferences Performance tab

and change the Scratch Disc to somewhere other than your system drive if you have the internal drives fitted.  If you only have 1 internal drive then leave “as is”.  You ‘could’ use an external drive as a scratch disk, but to be honest it really does need to be a fast drive over a fast connection – USB 2 to an old 250Gb portable isn’t really going to cut it!

You can go and check your Colour Settings, though these should not have changed – assuming you had ’em set right in the first place!

Here’s what they SHOULD look like:

Photoshop CC Update

Photoshop PROPER COLOUR SETTINGS!

That’s it – you’re done!

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This blog really does need your support. All the information I put on these pages I do freely, but it does involve costs in both time and money.

If you find this post useful and informative please could you help by making a small donation – it would really help me out a lot – whatever you can afford would be gratefully received.

Your donation will help offset the costs of running this blog and so help me to bring you lots more useful and informative content.

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Accurate Camera Colour within Lightroom

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Obtaining accurate camera colour within Lightroom 5, in other words making the pics in your Lr Library look like they did on the back of the camera; is a problem that I’m asked about more and more since the advent of Lightroom 5 AND the latest camera marks – especially Nikon!

UPDATE NOTE: Please feel free to read this post THEN go HERE for a further post on achieving image NEUTRALITY in Lightroom 6/CC 2015

Does this problem look familiar?

Accurate Camera Colour within Lightroom

Back of the camera (left) to Lightroom (right) – click to enlarge.

The image looks fine (left) on the back of the camera, fine in the import dialogue box, and fine in the library module grid view UNTIL the previews have been created – then it looks like the image on the right.

I hear complaints that the colours are too saturated and the contrast has gone through the roof, the exposure has gone down etc etc.

All the visual descriptions are correct, but what’s responsible for the changes is mostly down to a shift in contrast.

Let’s have a closer look at the problem:

Accurate Camera Colour within Lightroom

Back of the camera (left) to Lightroom (right) – click to enlarge.

The increase in contrast has resulted in “choking” of the shadow detail under the wing of the Red Kite, loss of tonal separation in the darker mid tones, and a slight increase in the apparent luminance noise level – especially in that out-of-focus blue sky.

And of course, the other big side effect is an apparent increase in saturation.

You should all be aware of my saying that “Contrast Be Thine Enemy” by now – and so we’re hardly getting off to a good start with a situation like this are we…………

So how do we go about obtaining accurate camera colour within Lightroom?

Firstly, we need to understand just what’s going on inside the camera with regard to various settings, and what happens to those settings when we import the image into Lightroom.

Camera Settings & RAW files

Let’s consider all the various settings with regard to image control that we have in our cameras:

  • White Balance
  • Active D lighting
  • Picture Control – scene settings, sharpening etc:
  • Colour Space
  • Distortion Control
  • Vignette Control
  • High ISO NR
  • Focus Point/Group
  • Uncle Tom Cobbly & all…………..

All these are brought to bare to give us the post-view jpeg on the back of the camera.

And let’s not forget

  • Exif
  • IPTC

That post-view/review jpeg IS subjected to all the above image control settings, and is embedded in the RAW file; and the image control settings are recorded in what is called the raw file “header”.

It’s actually a lot more complex than that, with IFD & MakerNote tags and other “scrummy” tech stuff – see this ‘interesting’ article HERE – but don’t fall asleep!

If we ship the raw file to our camera manufacturers RAW file handler software such as Nikon CapNX then the embedded jpeg and the raw header data form the image preview.

However, to equip Lightroom with the ability to read headers from every digital camera on the planet would be physically impossible, and in my opinion, totally undesirable as it’s a far better raw handler than any proprietary offering from Nikon or Canon et al.

So, in a nutshell, Lightroom – and ACR – bin the embedded jpeg preview and ignore the raw file header, with the exception of white balance, together with Exif & IPTC data.

However, we still need to value the post jpeg on the camera because we use it to decide many things about exposure, DoF, focus point etc – so the impact of the various camera image settings upon that image have to be assessed.

Now here’s the thing about image control settings “in camera”.

For the most part they increase contrast, saturation and vibrancy – and as a consequence can DECREASE apparent DYNAMIC RANGE.  Now I’d rather have total control over the look and feel of my image rather than hand that control over to some poxy bit of cheap post-ASIC circuitry inside my camera.

So my recommendations are always the same – all in-camera ‘picture control’ type settings should be turned OFF; and those that can’t be turned off are set to LOW or NEUTRAL as applicable.

That way, when I view the post jpeg on the back of the camera I’m viewing the very best rendition possible of what the sensor has captured.

And it’s pointless having it any other way because when you’re shooting RAW then both Lightroom and Photoshop ACR ignore them anyway!

Accurate Camera Colour within Lightroom

So how do we obtain accurate camera colour within Lightroom?

We can begin to understand how to achieve accurate camera colour within Lightroom if we look at what happens when we import a raw file; and it’s really simple.

Lightroom needs to be “told” how to interpret the data in the raw file in order to render a viewable preview – let’s not forget folks, a raw file is NOT a visible image, just a matrix full of numbers.

In order to do this seemingly simple job Lightroom uses process version and camera calibration settings that ship inside it, telling it how to do the “initial process” of the image – if you like, it’s a default process setting.

And what do you think the default camera calibration setting is?

Accurate Camera Colour within Lightroom

The ‘contrasty’ result of the Lightroom Nikon D4 Adobe Standard camera profile.

Lightroom defaults to this displayed nomenclature “Adobe Standard” camera profile irrespective of what camera make and model the raw file is recorded by.

Importantly – you need to bare in mind that this ‘standard’ profile is camera-specific in its effect, even though the displayed name is the same when handling say D800E NEF files as it is when handling 1DX CR2 files, the background functionality is totally different and specific to the make and model of camera.

What it says on the tin is NOT what’s inside – so to speak!

So this “Adobe Standard” has as many differing effects on the overall image look as there are cameras that Lightroom supports – is it ever likely that some of them are a bit crap??!!

Some files, such as the Nikon D800 and Canon 5D3 raws seem to suffer very little if any change – in my experience at any rate – but as a D4 shooter this ‘glitch in the system’ drives me nuts.

But the walk-around is so damned easy it’s not worth stressing about:

  1. Bring said image into Lightroom (as above).
  2. Move the image to the DEVELOP module
  3. Go to the bottom settings panel – Camera Calibration.
  4. Select “Camera Neutral” from the drop-down menu:
    Accurate Camera Colour within Lightroom

    Change camera profile from ‘Adobe Standard’ to ‘Camera Neutral’ – see the difference!

    You can see that I’ve added a -25 contrast adjustment in the basics panel here too – you might not want to do that*

  5. Scoot over to the source panel side of the Lightroom GUI and open up the Presets Panel

    Accurate Camera Colour within Lightroom

    Open Presets Panel (indicated) and click the + sign to create a new preset.

  6. Give the new preset a name, and then check the Process Version and Calibration options (because of the -25 contrast adjustment I’ve added here the Contrast option is ticked).
  7. Click CREATE and the new “camera profile preset” will be stored in the USER PRESETS across ALL your Lightroom 5 catalogs.
  8. The next time you import RAW files you can ADD this preset as a DEVELOP SETTING in the import dialogue box:
    Accurate Camera Colour within Lightroom

    Choose new preset

    Accurate Camera Colour within Lightroom

    Begin the import

  9. Your images will now look like they did on the back of the camera (if you adopt my approach to camera settings at least!).

You can play around with this procedure as much as you like – I have quite a few presets for this “initial process” depending on a number of variables such as light quality and ISO used to name but two criteria (as you can see in the first image at 8. above).

The big thing I need you to understand is that the camera profile in the Camera Calibration panel of Lightroom acts merely as Lightroom’s own internal guide to the initial process settings it needs to apply to the raw file when generating it’s library module previews.

There’s nothing complicated, mysterious or sinister going on, and no changes are being made to your raw images – there’s nothing to change.

In fact, I don’t even bother switching to Camera Neutral half the time; I just do a rough initial process in the Develop module to negate the contrast in the image, and perhaps noise if I’ve been cranking the ISO a bit – then save that out as a preset.

Then again, there are occasions when I find switching to Camera Neutral is all that’s needed –  shooting low ISO wide angle landscapes when I’m using the full extent of the sensors dynamic range springs to mind.

But at least now you’ve got shots within your Lightroom library that look like they did on the back of the camera, and you haven’t got to start undoing the mess it’s made on import before you get on with the proper task at hand – processing – and keeping that contrast under control.

Some twat on a forum somewhere slagged this post off the other day saying that I was misleading folk into thinking that the shot on the back of the camera was “neutral” – WHAT A PRICK…………

All we are trying to do here is to make the image previews in Lr5 look like they did on the back of the camera – after all, it is this BACK OF CAMERA image that made us happy with the shot in the first place.

And by ‘neutralising’ the in-camera sharpening and colour/contrast picture control ramping the crappy ‘in camera’ jpeg is the best rendition we have of what the sensor saw while the shutter was open.

Yes, we are going to process the image and make it look even better, so our Lr5 preview starting point is somewhat irrelevant in the long run; but a lot of folk freak-out because Lr5 can make some really bad changes to the look of their images before they start.  All we are doing in this article is stopping Lr5 from making those unwanted changes.

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Pixel Resolution – part 2

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More on Pixel Resolution

In my previous post on pixel resolution  I mentioned that it had some serious ramifications for print.

The major one is PHYSICAL or LINEAR image dimension.

In that previous post I said:

  • Pixel dimension divided by pixel resolution = linear dimension

Now, as we saw in the previous post, linear dimension has zero effect on ‘digital display’ image size – here’s those two snake jpegs again:

Andy Astbury,wildlife in pixels,pixel,dpi,ppi,pixel resolution,photoshop,lightroom,adobe

European Adder – 900 x 599 pixels with a pixel resolution of 300PPI

Andy Astbury,wildlife in pixels,pixel,dpi,ppi,pixel resolution,photoshop,lightroom,adobe

European Adder – 900 x 599 pixels with a pixel resolution of 72PPI

Digital display size is driven by pixel dimension – NOT linear dimension or pixel resolution.

Print on the other hand is directly driven by image linear dimension – the physical length and width of our image in inches, centimeters or millimeters.

Now I teach this ‘stuff’ all the time at my Calumet workshops and I know it’s hard for some folk to get their heads around print size and printer output, but it really is simple and straightforward if you just think about it logically for minute.

Let’s get away from snakes and consider this image of a cute Red Squirrel:

Andy Astbury,wildlife in pixels,

Red Squirrel with Bushy Tail – what a cutey!
Shot with Nikon D4 – full frame render.

Yeah yeah – he’s a bit big in the frame for my taste but it’s a seller so boo-hoo – what do I know ! !

Shot on a Nikon D4 – the relevance of which is this:

  • The D4 has a sensor with a linear dimension of 36 x 24 millimeters, but more importantly a photosite dimension of 4928 x 3280. (this is the effective imaging area – total photosite area is 4992 x 3292 according to DXO Labs).

Importing this image into Lightroom, ACR, Bridge, CapOne Pro etc will take that photosite dimension as a pixel dimension.

They also attach the default standard pixel resolution of 300 PPI to the image.

So now the image has a set of physical or linear dimensions:

  • 4928/300  x  3280/300 inches  or  16.43″ x 10.93″

or

  • 417.24 x 277.71 mm for those of you with a metric inclination!

So how big CAN we print this image?

 

Pixel Resolution & Image Physical Dimension

Let’s get back to that sensor for a moment and ask ourselves a question:

  • “Does a sensor contain pixels, and can it have a PPI resolution attached to it?
  • Well, the strict answer would be No and No not really.

But because the photosite dimensions end up being ‘converted’ to pixel dimensions then let’s just for a moment pretend that it can.

The ‘effective’ PPI value for the D4 sensor could be easily derived from its long edge ‘pixel’ count of the FX frame divided by the linear length which is just shy of 36mm or 1.4″ – 3520 PPI or thereabouts.

So, if we take this all literally our camera captures and stores a file that has linear dimensions of  1.4″ x 0.9″, pixel dimensions of  4928 x 3280 and a pixel resolution of 3520 PPI.

Import this file into Lightroom for instance, and that pixel resolution is reduced to 300 PPI.  It’s this very act that renders the image on our monitor at a size we can work with.  Otherwise we’d be working on postage stamps!

And what has that pixel resolution done to the linear image dimensions?  Well it’s basically ‘magnified’ the image – but by how much?

 

Magnification & Image Size

Magnification factors are an important part of digital imaging and image reproduction, so you need to understand something – magnification factors are always calculated on the diagonal.

So we need to identify the diagonals of both our sensor, and our 300 PPI image before we can go any further.

Here is a table of typical sensor diagonals:

Andy Astbury

Table of Sensor Diagonals for Digital Cameras.

And here is a table of metric print media sizes:

Andy Astbury

Metric Paper Sizes including diagonals.

To get back to our 300 PPI image derived from our D4 sensor,  Pythagoras tells us that our 16.43″ x 10.93″ image has a diagonal of 19.73″ – or 501.14mm

So with a sensor diagonal of 43.2mm we arrive at a magnification factor of around 11.6x for our 300 PPI native image as displayed on our monitor.

This means that EVERYTHING on the sensor – photosites/pixels, dust bunnies, logs, lumps of coal, circles of confusion, Airy Discs – the lot – are magnified by that factor.

Just to add variety, a D800/800E produces native 300 PPI images at 24.53″ x 16.37″ – a magnification factor of 17.3x over the sensor size.

So you can now begin to see why pixel resolution is so important when we print.

 

How To Blow Up A Squirrel !

Let’s get back to ‘his cuteness’ and open him up in Photoshop:

Our Squirrel at his native 300 PPI open in Photoshop.

Our Squirrel at his native 300 PPI open in Photoshop.

See how I keep you on your toes – I’ve switched to millimeters now!

The image is 417 x 277 mm – in other words it’s basically A3.

What happens if we hit print using A3 paper?

Red Squirrel with Bushy Tail. D4 file at 300 PPI printed to A3 media.

Red Squirrel with Bushy Tail. D4 file at 300 PPI printed to A3 media.

Whoops – that’s not good at all because there is no margin.  We need workable margins for print handling and for mounting in cut mattes for framing.

Do not print borderless – it’s tacky, messy and it screws your printer up!

What happens if we move up a full A size and print A2:

Red Squirrel 300 PPI printed on A2

Red Squirrel D4 300 PPI printed on A2

Now that’s just over kill.

But let’s open him back up in Photoshop and take a look at that image size dialogue again:

Our Squirrel at his native 300 PPI open in Photoshop.

Our Squirrel at his native 300 PPI open in Photoshop.

If we remove the check mark from the resample section of the image size dialogue box (circled red) and make one simple change:

Our Squirrel at a reduced pixel resolution of 240 PPI open in Photoshop.

Our Squirrel at a reduced pixel resolution of 240 PPI open in Photoshop.

All we need to do is to change the pixel resolution figure from 300 PPI to 240 PPI and click OK.

We make NO apparent change to the image on the monitor display because we haven’t changed any physical dimension and we haven’t resampled the image.

All we have done is tell the print pipeline that every 240 pixels of this image must occupy 1 liner inch of paper – instead of 300 pixels per linear inch of paper.

Let’s have a look at the final outcome:

Red Squirrel D4 240 PPI printed on A2.

Red Squirrel D4 240 PPI printed on A2.

Perfick… as Pop Larkin would say!

Now we have workable margins to the print for both handling and mounting purposes.

But here’s the big thing – printed at 2880+ DPI printer output resolution you would see no difference in visual print quality.  Indeed, 240 PPI was the Adobe Lightroom, ACR default pixel resolution until fairly recently.

So there we go, how big can you print?? – Bigger than you might think!

And it’s all down to pixel resolution – learn to understand it and you’ll find a lot of  the “murky stuff” in photography suddenly becomes very simple!

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Lightroom Tutorials #2

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Image Processing in Lightroom & Photoshop

 

In this Lightroom tutorial preview I take a close look at the newly evolved Clone/Heal tool and dust spot removal in Lightroom 5.

This newly improved tool is simple to use and highly effective – a vast improvement over the great tool that it was already in Lightroom 4.

 

Lightroom Tutorials  Sample Video Link below: Video will open in a new window

 

https://vimeo.com/64399887

 

This 4 disc Lightroom Tutorials DVD set is available from my website at http://wildlifeinpixels.net/dvd.html